Fluid seals assemblies of various types are used in numerous applications including and not limited to sealing vehicular engine crankshafts, transmission shafts, bearing lubrication systems, compressor shaft support assemblies, and the like. The fluid seal assembly is designed to retain and seal oil or grease in a predetermined location for lubricating the shaft and to prevent ingress of environmental contaminants.
Typical fluid seal assembly includes a casing unit, a flexible sealing member having a sealing lip adapted to engage against a sealing surface of a relatively rotatable member, such as the shaft. The flexible sealing member includes a body portion extending to an annular flex portion of reduced cross-sectional thickness bonded to the metal case member and located intermediate the seal lip and metal case. The purpose of this flex section is to allow the seal lip to stay in continuous, intimate contact with the shaft it is to seal despite any lack of concentricity between the relatively rotating members, e.g. the rotating shaft and the stationery engine block into which the annular metal case member is installed.
It is important to constantly retain and seal oil or grease in a predetermined location for lubrication of the shaft and to prevent ingress of environmental contaminants. There are numerous prior art seal assembly designs, which are effective to return oil or other lubricant to the sealed cavity upon rotation of the shaft. In either case, relative motion between the shaft and the seal assembly serves to “pump” the oil, grease, or other sealed fluid back into the sealed region defined between the shaft and the seal assembly.
The art is replete with various prior art references related to numerous seal designed to be adaptable to retain and seal oil or grease in a predetermined location for lubrication the shaft. These prior art references include and are not limited to U.S. Pat. No. 3,929,340 to Peisker; U.S. Pat. No. 4,336,945 to Christiansen, et al.; U.S. Pat. No. 4,501,431 to Peisker et al., U.S. Pat. No. 4,667,968 to Nash et al., U.S. Pat. No. 4,886,281 to Ehrmann et al.; U.S. Pat. No. 4,969,653 to Breen, U.S. Pat. No. 6,213,476 to Chandler et al., U.S. Pat. No. 6,620,361 to Longtin et al., and U.S. Pat. No. 6,736,404 to Shuster.
The U.S. Pat. No. 4,336,945 to Christiansen, et al. teaches a seal assembly for creating a fluid seal between first and second, relatively movable elements, at least one of which is arranged for rotation about an axis. The seal has a mounting portion thereof adapted to be fixedly associated in use with said first element, a dirt exclusion portion and an oil retention portion. The dirt exclusion portion has a plurality of annular excluder lips, and the excluder lips, as manufactured, extend radially inwardly and are spaced axially apart from each other. The lips also have an inside diameter substantially smaller than that of said second relatively movable element, and the excluder lips, in position of use, contact and lie along the second element, as installed, the lips are flexed so that the inner portions thereof extend radially inwardly as well as axially away from the region to be sealed.
The seal assembly taught by the U.S. Pat. No. 4,336,945 to Christiansen, et al. has several problems. The hydrodynamic features, such as spirals, are formed into the wafer portion of the seal, which contacts with the countersurface, i.e. the rotatable shaft. The location of the spirals or grooves results in clogging of these spirals or grooves with carbonized oil thereby reducing the lifespan of the seal assembly. Another problem is static leakage of oil through these spirals or grooves. Still another major problem associated with the seal assembly is a constant frictional engagement between the lip portion and one of the elements, the rotatable shaft rotatable about the axis. Due to wear and tear of the lip portion resulting from this constant frictional engagement, the seal assembly needs to be replaced.
The U.S. Pat. No. 6,620,361 to Longtin et al. discloses another design of the seal assembly that was intended to solve the problems associated with the prior art design, such as, for example, the seal assembly taught by U.S. Pat. No. 4,336,945 to Christiansen, et al. The U.S. Pat. No. 6,620,361 to Longtin et al. teaches a lip-type fluid seal assembly having a rigid annular case or carrier, a fluid seal having an annular sealing member carried by the case. The sealing member is made of any suitable elastomeric material. The sealing member has an annular body portion fixed to the flange of the case, and an annular flex section extending radially outwardly from the body portion at an axially outward inclination, terminating in an annular lip providing a sealing lip edge.
The U.S. Pat. No. 6,620,361 to Longtin et al. further discloses a non-elastic insert formed of PTFE material which is relatively harder than the material of the sealing member. The insert has an annular lip providing a sealing lip edge. The elastomeric and PTFE lip edges are adapted to sealingly engage a cylindrical sealing surface of a rotatable member. Together the lip of the sealing member and the lip of the insert provide an annular sealing lip of composite construction. The composite sealing lip is intended to protect against contaminants such as dust, dirt, sand, road grime, salt, water, etc. from entering the fluid side. The elastomeric lip may solve a problem of wear and tear of the sealing lip resulting from constant frictional engagement with the rotatable member, it fails to teach any features that provide bidirectional hydrodynamic functions.
Hence, there is a need for an improved fluid seals and methods to eliminate problems associated with prior art designs such as static leakage of oil, clogging up the seals with carbonized oil, constant wear and tear and replacement of parts that negatively impact lifecycle of the fluid seals. The inventive concept as set forth further below improves the aforementioned prior art systems and methods.